1. Field of the Invention
This invention relates generally to raceways for carrying cables, and more particularly to raceways for carrying cables across interior and/or exterior spaces. The raceway of the present invention provides at least one main channel member supported at each end by a support channel member, wherein the main channel member and the support channel member have respective covers. The raceway of the present invention also includes features that cause it to be compliant with motion due to, e.g., loading, seismic activity, meteorological activity, or thermal expansion, thereby making the raceway especially suitable for use on external structures such as bridges or the like.
2. Background
Various structures and methods have been used for carrying cables across interior and/or exterior spaces. For example, standard cable hangers have been used for stringing electrical cables. Such standard cable hangers normally cannot be used with, e.g., fiber optic cables because fiber optic cables typically lack the intrinsic strength found in most electrical cables. Accordingly, raceways or other channel structures have been used for carrying fiber optic cables or the like across interior and/or exterior spaces.
In U.S. Pat. No. 5,271,585 issued Dec. 21, 1993, to Zetena, Jr., a raceway for carrying fiber optic cables through interior spaces, e.g., offices, is described. In accordance with the disclosure, the fiber optic cable raceway includes a plurality of channel members and a plurality of telescoping members. Each channel member has a generally U-shaped cross-section with a base and sides with inwardly extending lips at the top. The telescoping members have the same generally U-shaped cross-section. However, the telescoping members are slightly larger than the channel members so that they can fit about the channel members in a longitudinally sliding fashion. By alternately interfitting the channel members and the telescoping members and adjusting the length by telescopic sliding, a cable raceway of a desired length can be quickly assembled. Further, the channel members may be enclosed with covers having downwardly extending legs that are spring-pressed outwardly to fit between the inwardly extending lips of the channel members. The channel covers can also telescope using telescoping cover members, which are slightly larger than the channel covers and have a complementary shape so that they fit about the channel covers in a longitudinally sliding fashion.
In U.S. Pat. No. 3,042,351 issued Jul. 3, 1962, to Du Bois, a cable tray assembly for carrying electric power cables in suspended positions about an industrial installation is described. According to the disclosure, the cable tray assembly includes a pair of abutting tray members, each being formed from a planar sheet of metal. Further, each tray member includes expanded areas for providing tray ventilation and reducing the overall weight of the cable tray assembly; and, non-expanded areas for providing structural support along edges, a central floor section, and corner portions of the tray member. In one embodiment of the cable tray assembly, respective strap members are coupled to the tray members for connecting the pair of tray members together at their abutting edges. Slots are also provided in a portion of the strap members for adjustable mounting of the strap members to the tray members.
Similarly, German Patent 2 353 471 published Oct. 22, 1973, discloses a structure with a plurality of elongated slots through which respective bolts extend for mounting a raceway to an intermediate bracket.
In U.S. Pat. No. 2,470,788 issued May 24, 1949, to O""Brien et al., an electrical conduit system for installation in buildings such as residential houses and industrial plants is described. In accordance with the disclosure, the electrical conduit system includes a plurality of severable conduit sections, which include a plurality of mutually abutting, rectilinearly extending channel members. Pairs of abutting channel members are held in alignment by a close-fitting sleeve, which slides over the abutting channel members. Further, the cross-section of the channel members includes a step configuration on the inner surfaces of the sides of the channel members.
Although each of the structures described above is suitable for carrying cables across interior spaces in, e.g., residential or industrial installations, it would be desirable to have a cable raceway that is suitable for carrying cables across exterior spaces, particularly, for external use on bridges or the like. Such a cable raceway would be strong, weather resistant, and easy-to-install and maintain. It would also be desirable to have a cable raceway that is not only strong but also compliant with motion due to, e.g., loading, seismic activity, meteorological activity, or thermal expansion, which normally affects bridges and like structures.
In accordance with the present invention, a cable raceway includes a series of support channels and a plurality of main channels. Each main channel is disposed between a respective pair of successive support channels. Further, the plurality of main channels is conterminous with the series of support channels, with end portions of each main channel disposed in overlaying relationships in the respective pairs of successive support channels. Each end portion of a main channel has an elongated slot formed therethrough; and, spacers attached to the respective pairs of successive support channels are disposed in the elongated slots, thereby allowing the end portions of each main channel to move with multiple degrees-of-freedom.
In another embodiment, the cable raceway is installed by attaching the first channel members to respective support members; disposing the end portions of each second channel member in the respective pairs of successive first channel members, thereby making the second channel members conterminous with the first channel members; coupling the end portions of each second channel member to the respective pairs of successive first channel members; laying cable in the conterminous first and second channel members; setting the second channel member covers over respective second channel members; and, setting the firs t channel member covers over respective first channel members.
In still another embodiment, the cable raceway further includes a plurality of support channel covers, each support channel cover being set over a respective support channel; and, a plurality of main channel covers, each main channel cover being set over a respective main channel. Each support and main channel cover includes a top portion; a pair of opposing sides extending downward perpendicularly from the top portion; and, a pair of steps, each step being formed on an inner surface of a respective side adjacent to the top portion and extending longitudinally along at least a portion of the length of the channel cover. The steps of each channel cover rest on respective edges of sides extending upward perpendicularly from a base of a respective channel.
The cable raceway of the present invention is particularly useful for carrying cables, e.g., fiber optic cables, across existing, external structures such as bridges or the like.
Still further aspects and advantages will become apparent from a consideration of the ensuing description and drawings.